Heat the oil in a large pan. Put the squash in a bowl with a splash of water. Cover with cling film and microwave on High for 10 mins or until tender. Meanwhile, add the onions to the hot oil and cook for a few mins until soft. Add the curry paste, tomatoes and coconut milk, and simmer for 10 mins until thickened to a rich sauce.
Warm the naan breads in a low oven or in the toaster. Drain any liquid from the squash, then add to the sauce with the lentils, spinach and some seasoning. Simmer for a further 2-3 mins to wilt the spinach, then stir in the coconut yogurt. Serve with the warm naan and a dollop of extra yogurt.